A 12 m long rectangular plate 1 m wide has a uniform air flo

A 1.2 m long rectangular plate (1 m wide) has a uniform air flow parallel to its surface (flow direction is along the length of the plate). The air flow is at 8.4 m/sec and 17 degree C with a corresponding uniform convection heat transfer coefficient of 48 W/m^2.K. The plate surface temperature is 70 degree C. Evaluate the heat transfer rate from the plate to the flow. Evaluate the heat transfer rate for a second, similar 1.6 m long plate (1 m wide) with a surface temperature of 90 degree C if the corresponding air flow conditions arc 6.3 m/sec and 17 degree C. Use free stream temperature as the reference temperature for evaluating fluid properties in both cases.

Solution

Answer 3 a) Given Data

length (l) = 1.2 m

wide (b) = 1 m

T₁₌ 17 C

T₂ = 70 C

h= 48 W/m²K

For convective heat transfer (Q) = hA (T₂-T₁)

Where A = Area

Here A = 1.2 ×1 = 1.2 m²

Q= 48×1.2×1× (70-17)

   = 3052.8 W (Answer)

Answer 3 b) Given Data

length (l) = 1.6 m

wide (b) = 1 m

T₁₌ 17 C

T₂ = 90 C

h= 48 W/m²K

For convective heat transfer (Q) = hA (T₂-T₁)

Where A = Area

Here A = 1.6 × 1 = 1.6 m²

Q= 48×1.6×1× (90-17)

   = 5606.4 W (Answer)